Water district explores water storage options with regional partners

Last month the Santa Clara Valley Water District Board of directors approved a cost share agreement with neighboring water agency Contra Costa Water District (CCWD) to explore the possibility of diversifying our water supplies.

Our water district will contribute $100,000 toward studies for the potential expansion of Los Vaqueros Reservoir in East Contra Costa County. This effort will consist of preparing a draft supplemental Environmental Impact Statement/Environmental Impact Report (EIS/EIR) and an application for Proposition 1 funding for the expansion project.

The Los Vaqueros Expansion Project would raise the reservoir dam to increase storage capacity by 115,000 acre feet; one acre foot is roughly the amount of water used in a year by two families of five. Located near the Alameda-Contra Costa County line, the Los Vaqueros Reservoir is an “off-stream” reservoir, meaning there are no significant rivers that flow to and from the body of water. The reservoir stores water diverted from the Sacramento-San Joaquin Delta. The advantage of off-stream reservoirs is that they minimize environmental impacts compared to the more conventional on-stream reservoirs.

The total cost of the project is estimated at approximately $800 million, with the potential to have up to 50 percent of the project financed by Proposition 1 funding.

Proposition 1 is a bond measure approved by California voters in 2014 to fund investments in water projects and programs. Water management agencies can solicit funding in key areas that contribute to a statewide, comprehensive sustainable water system. Such funding categories include regional water reliability, water storage capacity, water recycling, groundwater sustainability, safe drinking water and watersheds and flood management.

In addition to our water district, some potential partners include the United States Bureau of Reclamation, San Francisco Public Utility Commission, and East Bay Municipal Utilities District.

An enlarged Los Vaqueros Reservoir provides an opportunity to capture surplus water that would ordinarily flow into the ocean. The expansion project could benefit partnering agencies by allowing partners to store this surplus water supplies for use during drier years.

In addition to enlarging the reservoir, the project seeks to connect Los Vaqueros Reservoir to the South Bay Aqueduct system that our district uses to receive Delta water supplies allocated through the State Water Project. The connection to the South Bay Aqueduct would provide an alternate route for transmitting Delta water supplies during periods when regulatory requirements restrict flow through normal channels due to impact on endangered fish species.

Developing additional water supply resources and storage are key to our county’s growing needs. Over 40 percent of our imported water supply comes through the Delta, where the San Joaquin and Sacramento rivers meet. The Delta provides water to more than 30 million Californians and faces a looming need for restoration. Facing risk from aging levees, sea level rise, threatened ecosystems, and increased human and environmental demands, there are currently two large Delta restoration proposals pending further study. Diversifying our water resources with the Los Vaqueros Expansion Project is one way to bolster water supply reliability, especially considering the Delta’s water reliability and ecological challenges. However, it does not replace our need for a stronger and more reliable Delta water delivery system.

With the cost share agreement, staff will coordinate with CCWD to evaluate cost and benefits, and determine a level of participation. The project’s environmental documents and Proposition 1 funding application could be completed as early as June 2017. Santa Clara Valley Water District is also exploring other options for storage with other regional agencies.